In the present manufacture process of liquid crystal display (LCD), some manufacturers use the gate driver on array (GOA) technique to manufacture shift registers; and thus, the dependence on the mass materials of drive integrated circuit for the LCD panel can be avoided and consequently the manufactured shift registers can have a compact (for example, a lighter, thinner, shorter and smaller) design.
Several various types of thin film transistors (TFT) can be used in the GOA for the manufacture of the shift registers, and each type of TFT has specific advantages and disadvantages. For example, the amorphous silicon thin film transistor (a-si TFT) has a better homogeneity but has a relatively poor electro-mobility; and thus, the required layout area is relatively large if the a-si TFTs are adopted for the manufacture of the shift registers. Today, the amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFT), having an electro-mobility higher than the a-si TFT has, have been widely used in the GOA for the manufacture of the shift registers. However, both the a-si TFT and the a-IGZO TFT have specific problems while being as one of the circuit component in the GOA.
For example, due to the characteristic of the a-si TFT or the a-IGZO TFT, a biased turned-off voltage may occur while the GOA is turned-off (the turned-off voltage of TFT is about 0V), and the biased turned-off voltage may further result in a higher current leakage, the ripple issues or even cause the shift register having an unexpected output. Moreover, due to the current leakage of the TFTs, the GOA may have reduced recharge ability while the GOA is turned-on. Although the current leakage and the ripple issues can be avoided by increasing the number of the voltage regulator circuit in the shift register, due to the shift register accordingly has a relatively large circuit layout area and a higher cost; and thus, the shift register cannot have a compact design.